Beam Dynamics Design of a Radio-Frequency Quadrupole and a Drift Tube Linac for a High-Intensity Proton Injector

Abstract

We show the design results of beam dynamics on the injector for high-intensity proton accelerators. The injector can be utilized in a medical proton linac and accelerator driven system. The injector system consists of a 325-MHz RFQ (radio-frequency quadrupole) accelerator and a 325-MHz DTL (drift tube linac) accelerator. The injector has been designed to optimize the beam parameters to meet the required design goals. In this paper, we present a design study on the beam dynamics in the injector through beam tracking. We show the results of the beam dynamics study and cavity design study in the RFQ. The high-intensity RFQ accelerates the proton beam from 50 keV to 3 MeV with a peak beam current of 30 mA. The RFQ has a length of 3.839 m and Kilpatrick value of 1.76. We investigated ways to minimize the emittance growth caused by the space-charge effect and optimized achieve a high transmission and a small growth of emittance along the RFQ. The DTL with face angles of 3 degree and 10 degree in one tank accelerates proton beams from 3 MeV to 10 MeV and is 4.3 m long. Electromagnet quadrupoles (EMQs) are used as focusing elements in a Focusing-Defocusing-Focusing-Defocusing (FFDD) lattice scheme in the DTL. A quadrupole between the RFQ and the DTL, and 8 drift tubes (DT) in DTL are used for transverse matching in the DTL. We investigated the beam dynamics to achieve a high transmission and a small growth of emittance along the DTL. We also show the results of beam tracking simulations in the DTL. Our studies show that major parameters affecting on beam dynamics in the injector for a high-intensity proton linac are available.